Significance Unlike some species, such as the cow, primate oocytes must be matured in vivo in order to recover oocytes that are developmentally competent. This requires multiple injections of human gonadotropins (FSH and CG). Maturation of oocyte in vitro would help to conserve this expensive resource and serve as a model for similar protocols for women. Objectives There have been only anecdotal reports of live births resulting from cryopreserved human oocytes and no reported success in non-human primates. Reliable methods for oocytes freezing would enhance the to ability to perform primate research in the areas of fertilization and embryo development and would also provide a method to preserve oocytes from important individual animals. Frozen oocytes could also be shipped and allow stockpiling of oocytes for experiments that require large numbers, such as cloning. Results We currently have 10 animals assigned to the project that we are stimulating with recombinant human FSH so that multiple oocytes can be recovered. We have standardized our stimulation protocols and media. We have begun experiments to determine if we can maintain good fertilization rates and embryo development in culture if we replace the in vivo hCG injection with exposure of the immature oocytes to gonadotropins or granulosa cells in culture. In addition to in vitro maturation, this project will also focus on developing methods for cryopreservation of oocytes. Future Directions We will begin cryopreservation experiments with macaque oocytes later this year. One of the major goals is to determine if stage of oocyte maturation has an effect on the success rate of oocyte cryopreservation and subsequent thawing and development. KEY WORDS oocyte maturation, cryopreservation FUNDING NIH Grant RR13439